Telephone system



A ril 14, 1931. N. H. SAUNDERS ET AL TELEPHONE SYSTEM Original FiledApril 16, 1928 5 Sheets-Sheet l MQQEQEKR -ITLUETL2U'!" 5 Norman H 5 aunders Elarence E.Lumax April 1931- N. H. SAUNDERS ET AL 1,800,321

TELEPHONE SYSTEM Original Filed April 16, 1928 5 Sheets-Sheet 2 nuan ors Narman H.5aunder's Elar'euca E.Ln max M 4* 1 Wu April 14, 1-931. N,SAUNDERS ET AL 1,800,321

TELEPHONE SYSTEM Original Filed April 16, 1928 5 Sheets-Sheet 5 mImreniur Nurmau H. Saundars E Zar encsE Lumax N H, SAUNDERS ET AL,1,800,321

April 14, 1931.

TELEPHONE SYSTEM '5 Sheets'Sheet Original Filed April 16, 1928 QQ E i bR. I N 3% \R 9% 5w fiw Irma-n ur's Norman H. Saunders ElareuceE.LDT1'L&X

April 14, 1931. N. H. SAUNDERS ET AL 1,300,321

TELEPHONE SYSTEM Original Filed April 16, 1928 5 Sheets-Sheet 5 Imreu0P5 Norma-n .Eaun ars lavenceELnmax Patented Apr. 14, 1931 OFFICE NORMANH. SAUNDERS, 0F I-IOIVIEWOOIJ, AND CLARENCE I]. LOMAX, OF OAK PARK,

ILLINOIS, ASSIGNORS T0 RESERVE HOLDING GOMPZLNY, OF KANSAS CITY,MISSOURI,

trnnnriacnn sYs'rnM Application filed April 16, 1928, Serial No.$370,188. Renewed September 15, 1930.

v The present invention relates to telephone systems in general, but isconcerned more particularly with semi-automatic telephone systems, andthe main object, broadly stated, is the production of a semi-automatictelephone system wherein a common group ofsende'rs may be'used bysemi-automatic operators in a centralized exchange in setting upconnections from local lines and in setting up connections from lines ofremote semi-automatic exchanges.

Another object is to provide distributing apparatus at a semiautomaticoperators switchboard, which operates in conjunction with senderselectors for connecting the operators equipment automatically with anysender whichhasb'een selected by a sender selector so that'the operatormay ascertain the desired number and operate a sender to control theautomatic switches to'set up the desired connection.

- A further object of the invention is the production of suitablearrangements, efi'ee tive in connection with calls set up in a remoteexchange by an operator over an operating trunk, controlled from theoperating point over the operating trunkto disconnect the operatingtrunk from'the established connection and to place such connection underthe control of the calling subscriber without momentarily opening thesetting circuit of the switches, as this would result in a failure ofthe ringing equipment in a reverting call. I

This object is accomplished by providing a differential relay with onewinding connected in each leg of. the simplex operating circuit togetherwith means in thecentralized operating exchange for 'unbalancing-thesimplex circuit to switch theconnection through by operating thediilerential relay at the correct time i A further object of theinvention is to produce suitable arrangements whereby the release of theconnection in the remote ex change is left under the control of thecalling subscriber until an idle sender has been actually selected inthe centralized operating exchange and for then temporarily removing thecontrol of the release from the calling subscriber and for holding theconnection in a locked condition until the desired number has been setup and the sender hascompleted its sending operation. This latter objectis accomplished by means of a counting device under the control of theabove-mentioned dif f-erential relay and in connection with suitablecooperating circuit arrangements in the centralized exchange.

A further-object of the invention is the provision of practical andeconomical circuit arrangements for putting a system of the foregoingcharacter into successful opera-. tion.

Other objects and features of the invention will appear as thedescription which is to follow is perused.

ammz description Referring now to the drawing comprising Figs. 1-5, theyshow by means of the usual circuit diagrams, a suiiicient amount ofapparatus in a telephone system embodying the features of the inventionto enable the same to be understood.

Referring now particularly to Fig. 1, this drawing shows equipmentlocated in a remotely controlled semi-automatic exchange, connected withthe control point by the single operating trunk shown in the lower righth and corner of the drawing. The equipment shown includes the line ofsubstation T1, which terminates at the exchange in the automatic lineswitch LS1, which has access to selectors among which is selector switchS1. The trunkcircuit TCl is associated with the trunk line leading toselector S1, and it is through this trunk circuit that the trunk finderTF, in which the operating trunk terminates', is associated with thetrunk line to enable the automatic switches to be controlled to set upconnections.

Referring now particularly to Fig. 2, this drawing shows apparatuslocated in a semiautomatic exchange which is the control point fromwhich several outlying remotelycontrolled semi-automatic exchanges, suchas the one shown in Fig. 1, may be controlled. The equipment shown inFig. 2 includes aline of sub-station T2, which terminates at theexchangein the line switch LS2, having access to first selectors, one of whichis the selector S2. The trunk circuit T02 with which the sender SelectorSS1 is associated is inserted in the trunk line between the bank of theline switches and selector S2 for the purpose of enabling an associationto be made between the trunk line and an idle sender so that theoperator can control the automatic switches to set up desiredconnections. The operating trunk incoming from the remote exchange shownin Fig. 1 terminates in the lower left hand corner of Fig. 2 in therepeating coil and associated relays which cooperate with the senderselector SS2 to associate the operating trunk with an idle sender when acall arrives over the operating trunk.

The apparatus shown in Figs. 3, 4 and 5, includes the operatorssender-controlkey set and associated relays, shown in Fig. 3, and one ofthe four senders shown in the remaining portion of Fig. 3 and in Figs. 4and 5. The portion of the sender shown in Fig. 3 includes the relays311-314, while the registering portion is shown in Fig. 4 and thesending portion is shown in Fig. 5. The layout of apparatus is such thateach semi-automatic operator is provided with tour senders, the senderselectors, Fig. 2, which are usually 25-position mechanisms, have accessto senders of several operators.

Detailed description The apparatus having been described generally inthis manner, a detailed description of its operation will now be given.For this purpose it will be assumed the subscriber at sub-station T2,Fig. 2,'desires a connection to be set up from his line to the line ofanother local subscriber whose number is, for example, 5326.

Gonnection set up in centralized exchange When the receiver is removedat station T2, the line switch LS2, the circuit of which are not shown,operates in the usual manner to select an idle'trunk, which trunk, itwill be assumed, is the one comprising conductors 214- 216. lVhen thistrunk is seized,line relay 201 thereof operates over the calling lineand at its upper armature places ground on the release trunk conductor215 so as to guard the trunk line from intrusion and to maintain theline switch LS2 operat d. At its inner lower armature, relay 201 closesa circuit for switching relay 203 in series with the associatedoperating magnet of the senderselector SS1. At the same time, relay 201,at its lower armature, connects test wiper 206 to the unction of relay203 and the operating magnet, with the result that the sender selectorsearches for an idle trunk in the usual man- Sender selection Assumingthat the trunk line comprising conductors 209213 and extending to thesender shown in Figs. 3-5 is the one found to be idle, switching relay203, which is short circuited as long as a ground potential isencountered by test wiper 206, energizes in series with the associatedoperating magnet, which magnet does not operate at this time on accountof the relatively high resistance of relay 203. At its inner lowerarmature, relay 203 disconnects test wiper 206 from the junction of thewinding of relay 203 and the operating magnet and connects the wiper toground, thereby placing a guarding and holding potential on conductor211. At its remaining contacts, relay 203 connects up the remainingwipers on the switch SS1. As a result of impulse wiper 207 beingconnected up at the middle upper armature of relay 203, the upperwinding'of line relay. 221 of the selector S2 is energized over theupper talking conductor and over conductor 213 extending to the senderacross Figs. 3 and 4 to ground through contacts of the interrupter I inFig. 5. Upon operating, relay 221 closes a circuit for release relay222, which operates to prepare the switch for operation- In the selectedsender, relay 311 operates over the grounded release-trunk conductor 211and through contacts of relay 312 and at its lower armature disconnectsthe corresponding test conductor from ground and extends it to the #1connecting relay 308. This is preparatory to enabling the distributor Dto stop on a contact associated with the #1 sender and operate the #1connecting relay so as to connect the #1 sender with the operatorsequipment. At its upper armature, relay 311 places ground on theassociated start operating slow-acting relay 304: through contacts ofrelays 305308. Relay304 closes a circuit for the associated relay 303,which relay operates and starts the hunting action of the distributor Dby connecting test wiper 325 to stepping magnet 324-. throughtheselfinterrupting contacts of the stepping magnet. At its two upperarmatures relay 303 disconnects common'conductors 326 and 327 from theoperators headset and connects the conductor 327 through the associated;condenser to the differential tone generating relay. Each time relay 302pulls up and closes a circuit for its upper winding in parallel with itslower winding, it falls back dueto the differential relation between itstwo windings, thereby generating a tone current which is impressed onconductor 327 through the associated condenser. This tone current ,isnotsent back to the calling line for the time being.

The test wiper 325 of the distributor D encounters a ground potential onthe test conping operation ceases due to the absense of a direct groundpotential on the test conductor and a circuit is closed for relay 308through test wiper 325 and the lower armature, operated of relay 311,from battery through stepping magnet 324 and the lower contacts of relay303. Operating magnet 324 does not operatively energize in series withrelay 308* owing to the relatively high resistance of the latter. Whenrelay 308' operates, it connects at certain of its lower armatures the20 six conductors associated with the operators key set to thecorresponding conductors of the sender; it closes a locking circuit forit self at its inner lower armature in multiple .25 with the lowercontacts of relay it lights the call lamp associated with the operatorskey set at its upper armature; connects up the conductors 209 and 210 atits intermediateupper armatures'to the common conductors 326 and 327;and at its upper armaturc it opens the circuit of slow-acting relay 304.During the time required for relay 304 to fall back after its circuitisopened, the tone generated by the differential tone relay 302 is heardby the calling subscriber, who is informed thereby that he may now givethe'desired number to the operator. Relay 304 falls back shortly andopens the circuit of relay 303 in addition to stopping 1 the generatingof tone current, whereupon relay 303 falls back and connects conductors326 and 327 to the operatorshead-set. At

the time this connection is made, the operciated talking condenser isequalized with thepotential diii'erence across conductors 326 and 327 soas to shield the operator from disagreeable noises in her head-set.Relay 301 falls back an instant later and places the operator intocommunication with the calling subscriber.

Registration of desired number Upon hearing the number desired by thecalling subscriber, which number, as hereinbefore assumed is 5326, theoperator depressed the digit keys of her key set forthe respectivedigits of the number. It will be noted that the four conductorsassociated with the digit keys are labeled A, B, C, and D. The operationof a given, key results, in the grounding of one or more of theseconductors. As an aid in reading the drawing, the conductors groundedresponsive to the operation of each key have beeii. noted in parenthesisabove each key.

*Vhen the operator depresses the #5 key to set up the first digitb, theB and D conductors are grounded, operating relays Bland D1 of thethousands register Fig. 4, relay 412 being operated at this time fromthe grounded release trunk conductor 211 through contact of releaserelay 314 and the inner upper con tacts of the transfer relay 411. Upon0p-- crating, relays B1 and D1 lock themselves to conductor 323 throughtransfer relay 411, but relay 411 does not operate until the initialcircuit of these relays is opened, being short circuited until thishappens.

When the key is released, relay 411 operates in series with relays B1and D1 (which latter relays remain operated) and at its inner upperarmature it disconnects the connecting relay 412, whereupon relays A1D1are disconnected from the conductors A.-D. At its upper armature, relay411 places ground on conductor 322 through contacts of relay 414,operating relay313, Fig. 3 to open a point in the switch through circuitto be hereinafter described and to place a multiple ground connection onrelease-trunk conductor 211. At its middle upper armature, relay 411extends a ground potential to the relays of the hundreds register,operating relay 422 to connect the conductors A, B, C, and D, to therelays A2, B2, C2, and D2, respectively. Now, When'the operatordepresses the #3 key to register the hundreds digit 3, conduc tors A.and D are grounded,operating relays A2 and D2. These relays lock up inseries with relay 423, which remains short circuited as long as the keyis depressed and operates as soon as the key is released. Relay 423. in

addition to extending a ground potential to the tens register to causerelay 432 to operate, disconnects relay 422 and places a furthermultiple ground connection on conductor 322.

When the tens digit 2 is registered by depression of the #2 key, relaysA3 and C3 are operated over conductors A and C, whereupon they lock upin series with relay 431, which relay operates when the key is releasedand transfers the control'to the units register 'by releasing relay432and operating Retransmissrion of number Having. finished setting up thenumber, the operator depresses the start key, whereupon start relay 312is operated through conpendulum swings to the left.

tacts of relay 308 and through the lower winding of relay 311 and closesa locking circuit for itself to conductor 211 at its inner upperarmature, at'the same time disconnecting the upper winding of relay 311.Relay 311 remains operated through its lower winding until the start keyis released where upon it falls back and opens the circuit of relay 308,at the same time replacing ground on the associated contacts in the bankof wiper 325 of the distributor D. Relay 308 falls back and disconnectswiper 325 from the associated operating magnet, at the same timesevering all connection between the operators common equipment and thesender #1 and closing the associated point in the chain circuit of startrelay 304 so as to enable the distributor D to operate again to connectthe operators head-set to another sender which may have been taken foruse in the meantime.

As a further result of the operation of start relay 312, it prepares theswitchthrough circuit, to be hereinafter described,

at its upper armature, and at its middle armature it places ground fromthe inner contacts of relay 313 on start conductor 321 so as to startthe stepping action of the counting switch CS, Fig. 5, under the controlof the marginal stepping relay 501 associated with the interrupter I. 7

It may be pointed out at this time that the interrupter I is firststarted into operation upon the seizure of the sender when the groundpotential is placed on release-trunk conductor 211. This results in aclosure of a circuit through the magnet winding of the interrupter I andthrough the'marginal stepping relay 501 in series. Relay 501 does notoperate in series with the magnet winding of the interrupter I, but uponthe energization of this magnet windin the weighted pendulum is drawnover to the right, short circuiting the magnet winding of theinterrupter whereupon the interrupter magnet deenergizes and thesteppingrelay 501 energizes. When the pendulum swings to the left it a ainincludes the ina met windin 'v of the interrupter in circuit, whereuponrelay 501 falls back. As the interrupter I continues to operate, theimpulse relay 501 is operated each time the pendulum swings to theright, and the interrupter contacts of the interrupter I are opened eachtime the Now, the operation of the interrupter I is ineffective, and theoperation of'stepping relay 501 is ineffective likewise until startconductor 321 is grounded as above described upon the depression of thestart key by the operator, from which time eachdeenergization ofstepping relay 501 results in an energization of the operating magnet ofthe counting switch CS from conductor 321 through contacts of stop relay503. The

wipers 504 and 505 on the counting switch OS are advanced only upon theback stroke of the operating magnet, and they consequently remain in theposition shown upon the first energization of the magnet. When thependulum of the interrupter I swings to the right and opens theoperating-magnet circuit by energizing stepping relay 501, the operatingmagnet falls back and advances the wipers 504: and 505 one step,whereupon pick-up wiper 504 encounters a'grounded contact, closing acircuit for pick-up relay 502. Pick-up relay 502 operates and prepares alocking circuit for stop relay 503 at its lower armature; places afurther multiple ground connection on conductor 322 at its upperarmature; and at its inner upper armature it removes one groundconnection from the outgoing impulse conductor 213, leaving theconductor grounded only through the contacts of the interrupter I.

Now, with the circuit in this condition, each time the pendulum of theinterrupter I swings to the left, it sends an impulse by removing groundfrom conductor 213 to de-energize the line relay of the selector S1,Fig. 1. The operating magnetis reoperated by the deenergization ofstepping relay 501 so that each time the pendulum swings to the rightrelay 501 reoperates and drops back the operating magnet to advancewipers 504: and 505 another step.

When the wipers ofthe counting switch are advanced again at the end ofthe transmission of the impulse, wiper 505 encoun ters the bank contactin which the first stop conductor terminates, which stop conductor isgrounded only in case the digit being transmitted is the digit 1. Thedigit being transmitted in this case is the digit 5, stored on thethousands register Th, Fig. 4, from which it follows that the #5conductor is grounded instead. of the #1 conductor.

The #5 conductor is grounded at this time through the lower armature,normal, of transfer relay 414:, Fig. 4, right hand armature, normal, ofrelay A1, outer armature, operated, of relay B1, middle armature,normal, of relay C1, and the associated armature, operated, of relay D1.That being the case, the sending operation continues and the advance ofthe counting switch CS continues until five impulses have been sent bythe interrupter I over the outgoing control circuit. At the end of thefifth impulse wiparmature; places a further multiple "ground connectionon conductor 322 at still another armature; and at its u per-mostarmature it disconnects the operating magnet from the impulse circuitcontrolled by stepping relay 501. v I

1 Responsive to the closure of the restoring circuit of the countingswitch GS at the inner upper contacts of relay 503, the selfinterruptingoperating magnet operates rapidly in a buzzer-like manner and the wipers504 and 505 are advanced until they stand in the position shown in thedrawing, whereupon the action ceases due to the fact that thenormalContact in the bank of wiper 504 is ungrounded. At this time the circuitof slow-acting pick-up relay 502 is opened, with the'result't hat therelay falls back shortly and opens the locking circuit of relay 503,which relay shortly falls back to start the transmission of the hundredsdigit 3.

When the circuit of stop relay 503 is first closed at the end of thetransmission of the thousands digit, a parallel circuit is closed overconductor 401 and through contacts of relay 414 for relay'413. Relay 413operates locks itself to conductor 323 in series with relay 414, whichlatter relay remains short circuited until the locking circuit of re lay-3 is opened by relay 502, whereupon relays 414 energizes in series withrelay 413 and transfers conductor 401 to relay 423 of the hundredsregister.

The sending operatlon proceeds for the second digit in the same manneras described inconn'ection with the first digit and is teri'ninated atthe end of the transmission of the third impulse upon the energizationof stop relay 5'03, when wiper 505 encounters the hank contact in whichstop conductor 3 terminates. The stop conductor #3 is grounded at thistime through contacts of relays 414 and 424 and through contacts of theoperated relays A2 and D2, in addition to the contacts ofthe unoperatedrelays B2and C2.

Belay 423 is energized at this time in multiple with the stop relay andlocks'itself in series with relay 424, which latter relay opcrates, whenthe circuit of the stop relay is opened and transfers conductor 401 torelay 433 of the tens register. The stopping ground potential is shiftedat the lower contact of relay 424 to the register relays of the tensregister.

W hen the retransmission of'the tens digit takes place, the operation isthe same as described hereinbef-ore until stop relay 503 operat es atthe end of the second interruption in the outgoing control circuit whenwiper 505 encounters the bank contact in which stop conductor #2terminates, stop conductor #2 being grounded at this time throughcontact of the operated relays A3 and C3 and contacts 011116non-operated relay B3. Re-

lays 433 and 434 are operated in a manner similar to relays 4 23 and424- to transfer the control'to'ithe unit register.

Thetransm-ission of the units-digit 6 next takes place andis-ter'minatecl upon the energization of stop relay 503 at the end ofthe 6th interruption in'the outgoing control circuit when wiper 505lands upon the bank contact in which stop conductorb terminates,

stop conductor 6 being grounded at this time through contacts of. thenon-operated relays A4 and B4 and contacts of theoperated relays C4 andD4. 1 Freeing the s-e'adw it will be noted that each of the relays 414,,424, 434, and 444., upon operating remoyes ground at one point from themultiplygroundedconductor 322. Now, when relay 444 operates upontheopening ofthe circuit of stow-acting stop relay 503, when pick-uprelay 502 falls back at the end of theunit digits, it leaves conductor322' grounded only at the contacts of stop relay 503. Now, when relay503 falls back at this time conductor is ungrounded at all points andrelay 3l-3, Fig. 3, falls back as a result. Belay 313r1emoves groundfrom start conductor, 321 at its inner armatureand at its upper armatureit removes ground at one point from conduc tOI 211 and Closes theswitch-through circuit through contacts of the operated relay 312 andover conductor 212. This circuit includes wiper 205 of the senderselector SS1, Fig. 2, the inner upper contacts of switching relay 203,and the switch-through relay202. Relay 202 operates'and locks itself toreleasetrunk conductor 215 at itsinner upper contacts, and at its upperand lower armatures it disconnects the incoming conductors 214 and 216from the line relay 201 and extends them to the corresponding conductorsof the connection established through the selector S2. Asa result. ofthis, line relay 201 falls back, followed by the fallingback of relay203 to disconnect the wipers of the sender selector SS1, to free thesender. The established connection is now held up over the line ofsub-station C2.

' Whe'nthe sender is freed, the removal of the ground potential fromconductor 2111 re: sults in the de-energization of relay 312, Fig. 3,and in the deenergization of relays 411-, 413, and 414, Fig. 4. As aresult of'the deenerization of relay 411, relays 421, 423, and 424 fallback and the "deenergization of relays 431, 433, and 434 follows, fromwhich follows thede-energization of relays 441, 443, and 444. Theoperation of the interrupter I ceases as a result of the removal of theground potential from conductor 211. Y

The sender is now at normal and may be seized again for use anothercall.

Setting the switches The response of the automaticswitching mechanism tothe impulse trains retransmitted by the sender will now be considered.Returning now to'the point at which the first series of impulses(interruptions) is trans: mitted to the upper winding of line relay 221of the selector S2, each time the circuit of this upper winding isopened at the contacts of the interrupter I, Fig. 5, line relay 221falls back and closes a circuit for the associated vertical magnetthrough the lower armature, operated, of relay 222 and the winding ofseries relay 223. By the operation of the vertical magnet the wipers226228 are raised step by step until they come to rest opposite thefifth level of bank contacts, the digit received being-the digit 5.Relay 223 energizes in series with the vertical magnet when the firstimpulse'is received, and, being slow acting remains operated throughoutthe series of impulses, Upon operating, relay 223 prepares a circuitfrom the grounded release trunk conductor 215 for relay 224, which isclosed as soon as the associated off-normal contacts have closed uponthe first vertical step. Upon operating, relay 224 prepares .a circuitfor themtary magnet at its lower armature and its upper armature closesa locking circuit for itself from theinner lower contacts of relay 228and including the associated rotary-magnet interrupter'contacts and theassociated off-normal contacts.

At the end of the vertical movement, relay 223 falls back and closes therotary magnet circuit, whereupon the rotary magnet operates and advancesthe wipers 226228 one step. If the trunk line terminating in the firstset of bank contacts is idle, switching relay 225 operates inseries withrelay 22 1 and seizes the trunk. Assuming, however, that trunk line isbusy, relay 225 is short circuited by the ground potential encounteredon the test contact by test wiper 227 and does not operate. Relay 224;operates again through test wiper 227, and the rotary magnet isreoperated to advance the wipers another step.

This alternate operationof stepping relay 22 1 and the associated rotarymagnet con-' tinues until an idle trunk line is reached,

relay 128.

slow acting" release relay 222 falls back a m0+ ment later. I 1Responsive to the transmission of the remaining digits, the remainingportion of the connection to the called line is set up in the well-knownmanner.

The established connection is held over the calling line and over thetwo local talking conductors in series after the connection has beenswitched through upon the operation of the switch through relay 202 ofthe trunk circuit TC2;

'ReZease of connection I The conversation between the called subscriberand the calling subscriber takes place in the usual manner when thecalled subscriber responds, and the connection releases in thewell-known manner when the subscriber at substation C2 replaces hisreceiver. The release of the switches LS2 and S2, as well as the trunkcircuit T62, it may be pointed out, takes place when the groundpotential is removed from the release trunk conductor of the establishedconnection by the final switch. When this occurs, switching relay 225 ofthe selector S2 and switchthrough relay 202 of the trunk circuit T02both tall back. The switching relay 225 closes the circuit of theassociated release magnet at its inner lower contacts, through the lowercontacts ofrelays 221 and 222 and through the associated oft-normalcontacts. By the operation of the release magnet the mechanism of theswitch is restored to its normal position, whereupon the oil-normalcontacts associated with the release magnet open the circuit thereof.

It will now be assumed that the subscriber at substation T1, Fig. 1,desires to converse with another subscriber whose lines terminates inthe same remote exchange and whose number is, for example, 914.

Connection set up in remote ewchcmge When the receiver is removed atsubstation T1, the line switch LS1 operates in the usual manner toselect an idle trunk, the trunk comprising conductors 112114:, forexample. When this trunk is seized, line relay 102 ene'r gizes over thecalling line and places ground on the first-level start conductor 119 atits upper armature. t its lower contacts relay 102 removes the guardingpotential from the associated test contact in the bank of the trunkfinder TF and prepares a holding circuit for l/Vhen the first-levelstart conductor 1 19 is grounded as above pointed out, a circuit isestablished through the associated resistance and over conductor 120 forstartrelay 129 through contacts of relay 127 and contacts of the releasemagnet. Start relay 129 operates and closes at its second armature fromthe bottom a circuit through the contacts of the verticalmagnet','contactsoi relay 131, con tacts of the rotary magnet and itsown lower contacts tor stepping relay 130. Relay 130 operates andcompletes a circuit for the vertical magnet at its lower contacts,whereupon the vertical magnet responds by raising the wipers121136 andthe test wiper 136 one step. The vertical magnet also opens the initialcircuit of stepping relay 130. In case there is no call waitin on thefirst level, this results in a deenergization of stepping relay 130 andin a further operation of the vertical magnet. In this case, however,the calling trunk is reached from the first level of the finder and testwiper 136 encounters a ground potential on the first level-test contactover the start conductor 119 with the result that relay 130 remainsoperated notwithstanding the opening of" the vertical magnet interruptercontacts. The new circuit includes normally closed contacts controlledby the inner lower armature of relay 131, the lower winding of relay131, vertical test wiper 136 on its first level contact, and thegrounded start conductor 119. Relay 131 operates in series with relay130 and closes a locking circuit for its upper winding through its uppercontacts at re lays 129 and 128.- Relay 131, at its lower armature,transfers themagnet-operating circuit from the vertical magnet to therotary magnet; while at its inner lower armature, it closes transferrelay 1301mm the vertical test wiper 136 to rotary test wiper 125. Relay130 is now held energized in a locking circuit including its own innerlower contacts and the middle lower contacts of relay 129.

When the rotary magnet operates, it advances the wipers1'121-.126 onestep into engagement with the first set of contacts in the first level,and it opens the circuit of relay 130. Relay 130 thereupon falls backand opens the circuit of the rotarymagnet and a further point in its owncircuit. ther operation depends upon whether the trunk line TClterminates in the first set of contacts in the level or in some otherset. It will be assumed that the latter is the case. iVhen rotary magnet130 falls back, it closes a circuit for relay 130 at its interruptercontacts through the third armature from'the bottomof relay 131, toground through test wiper'125 and the grounded test contact on which itis standing. It will be noted that the presence of this ground potentialis the i only thing which prevents the lower winding of relay 128 fromenergizing through the inner lower contact of relay 129 in series withrelay 130. Relay 130 reoperates and again closes a locking circuit foritself at its inner lower armature, at the same time again-operating therotary magnet to bring about a further advance of the wipers of theswitch.

This stepping operation of the trunk finder TF continues until thewipers land upon the contacts associated with the trunk circuit The furTCl, whereupon the action ceases due to the fact that there is no groundpotential on the test contact in the bank of Wiper 125 because linerelay 102 is operated. In this case, relay h 130 does not operatethrough the test wiper again and relay 128 energizes in series withrelay 130, but relay 130 does not operate again owing to the relativelyhigh resistance of the lower winding of relay 128. When relay 128operates, it closes a locking circuit for itself at its inner uppercontacts and over test w1per 12 4 and the contact 011Wll10l1 it 18standing and through the lower armature of line relay 102. At its middlearmature, relay 126 opens p the circuit of relay131, and at its lowerarmature it closes a circuit for relay127. Relay 127 operates and at itsinner upper armature opens the circuit of start relay 129, whereperarmatures and at its lower armature, relay 127 connects up wipers 121123and 126.

As a further result of its operation, above described, relay 128- at itsupper armature upon this relay falls back. At its three upconnectsimpulse relay 128 to the conductors through contacts of relay 127 andover wiper 123 to the upper winding of line relay 104 of the selector S1by way of contacts of relay 108. Relay 104 operates, followedby theenergization of relay 105 to prepare the selector S1 for operation.

' Differential relay 132 operates, because current is flowing throughonly one winding, and closes a circuit for the upper winding of twodim"its

step relay 133, which relay operates through v its first step. 7

In the centralized exchange, relay-241, upon operating over theoperating trunk as above mentioned, closes at its inner lower and middlelower armatures circuits for causing the sender selector SS2 to advanceunder the control of test wiper 249 in search of an idle sender in themanner hereinbefore described in connection with the sender selectorSS1. When an idle sender is found, the one .for example shown in Figs.3-5 and reached by way of conductors 209213, switching relay 245operates, and, in addition to grounding test wiper 249 at itsinner lowerarmature, connects up'wipers 247, 250, and 251 at its remainingarmatures.

Upon referring again to Fig. 1, it will be noted thatthe releaseof theconnection es tablished to the idle sender is under the con trol of thesubscriber at substation Tl'and that should he hang up his receiver atthis tion.

stage before communicating with-the operator, the connection wouldrelease responsive to the falling back of line relay 102 of the trunkcircuit TCl, which would be followed bythe deenergization of relays 128,127, and

132134 of the trunk finder TF and the release of the trunk finder. Inthe sender selector SS2, Fig. 2, relay 245 would fall back as a resultof the deenergization of relay 241. This is mentioned at thispoint owingto the fact that this condition will be changed as will be pointed outhereinafter. When wiper 250 is connected up, relay 244 energizes throughthis wiper from ground on impulse conductor 213, which is groundedthrough contactsat relay 502 of the sender. Relay 244 looks itselfenergized and transfers the incoming impulse conductors to wipe 250, atthe same time closing a local circuit for relay 241 through resistance246. Current now flows from the grounded conductor 213 Y and throughwiper 250 over both conductors of the operating trunk, whereupondifferential relay 134, Fig. 1, falls back and opens the initial circuitof the upper winding of relay 133, whereupon, the lower winding, whichhas been short circuited heretofore, energizes in series with the upperwinding and operates the relay through its second step. At this time,relay 133 at its lower armature, places the associated resistance inshunt of the talking condenser connecting the left-hand repeating coilwindings. This establishes a parallel circuit for line relay 102 so asto hold this relay energized independent of the calling party until theconnection has been set up.

Responsive to the grounding of release trunk conductor 211 of the senderthrough test wiper 249, relay 311, Fig. 3, operates as hereinbeforedescribed to cause the opera-' tors equipment to become connected withthe selected sender, and the interrupter I, Fig. 5, begins thehereinbefore-described opera- It will be remembered that theenergization of relay 311 is followed by the energization of relays 304and 303 and by the step-by-step operation of the distributor D whichresults in the distributor D landing upon the contact leading throughthe lower armature of the operated relay 311 to the #1 connecting relay308, and that the resulting operation of relay 303 is followed by thedeenergization of relays 304 and 303 whereupon the connection iscompleted from the calling line to the operators telephone after amomentary application of the current has been made to the calling lineto inform. the calling subscriber that the operator is waiting for thenumber. I Y

After learning the desired number from the subscriber, which number ashereinbefore assumed is 914, the operator depresses the #9 key, the #1key and the #4 key, one after the other, with the result that the digitsfirst digit is stored; that relay 421 operateswhen the second digit isstored; and that relay 431 operates when the third digit is stored. Whenthese three relays are operated, conductor 322 is grounded at threepoints. 'Relay 313, of course, is operated upon the first application ofground potential to conductor 322 when the digit 9 is stored.

Having set up the three digits in the called number, the operatordepresses the start key, Fig. 3, operating relay 312 to start the senderto operate and to disconnect the operator from the sender by releasingrelay 311' when the start key is closed. The sending apparatus of Fig. 5now operates responsive to the ground potential on start conductor 321and retransmits the stored digits 9, 1, and 4 in the hereinbeforedescribed manner. It

will be remembered that relay 413 of the potential is removed at thelast point from conductor 322. Relay 313 falls back and closes theprepared switch-through circuit (through the upper contactsof relay 312and over conductor 212) for switch-through relay 243, of the senderselector SS2, by way of wiper 248 and contacts of relay 245. Relay 243operates and locks itself through contacts of relay 241 and it opens thecircuit of relay 244 at its inner lower armature, whereupon relay 244falls back and transfers the upper conductor of the operating trunk backto relay 241 and again opens the lower conductor. When this-occurs,differential relay 134, Fi 1, pulls up again and, this time closes acircuit through contacts at relays 133 and 127, and through wiper 122for switch-through relay 103.

Relay 103 operates and locks itself to the associated grounded releaseconductor 113 at its inner upper armature, and at its upper and lowercontacts it switches the conductors connection with any subsequent:call.

through contacts of relay 129 and off-normal contacts, The releasemagnet operates and restores the finder to-its normal position in theusual manner, whereupon the release magnet circuit is opened at theassociated odnormal contacts, The contacts of the release magnetmaintain start relay 129 discon nected during the releasing operation.It

will be noted that the circuit for maintaining relay 129 disconnectedafter the finder has operated is taken through contacts of relay 127,.which is a slow acting relay and that the release magnet circuit isclosed. at the same timethat the circuit of relay 127 isopened.

Due. to the fact that relay 127 is slow acting the release magnet hastime to energize and disconnect relay 129 at a further point before theslow acting relay 127 falls back and closes the associated point in thecircuit of relay 129. This is of utility in case the start conductor isgrounded at the timethe release occurs, as it prevents the finder fromtrying to test while it is releasing. Relays 132-134 fall back whenrelay 12.8 restores. As a result of the opening of he upper contacts ofrelay 128, line relay 241, Fig. 2,'falls back and opens the circuit ofrelays 243 and 245,

which relays fall backand restore the associated circuit connec to norml- The operating trunk may now be used n The connection set up throughswitch LS1. and the Selector S1 is released in the usual manner when thecalling subscriber replaces his receiver after conversation. The releaseof the selector upon the falling back of relay 108 is brought about bythe energization of the release magnet of the selector when groundpotential is removedfrom the release trunk conductor of the establishedconnection, and the locked up switch-through relay 103 falls back at thesame time.

Referring again to Figs. 3 and 4, it may be pointed out that theoperator can release a partial registration by operating the release keyshown-in the lower left hand corner. of Fig. 3 in case she discoversthat she has made an error. When the rele-ase'key is operated, relay 314pulls up and disconnects the grounded conductor 211 from conductor 323,permitting the registering apparatus of Fig. 4 to restore to normal.Following this, the operator permits the release key to restore andproceeds to set up the number by operating her numberkeys in the usualmanner.

the line In case acall comes into the operator and no response issecured to the-momentary ap plication of tone current and to a challengeby the operator, she may cause the connection to be switched through-tothe first selector and therebyfree the sending equipment, by operatingher startkey without first setting.

up a number.. As an alternative, the opera tor may set up apredetermined number and cause the call to be trunked to a spec1alpos1-tion especially, equipped for handling false calls. This latterarrangement is usually preferable, it enables the attendant at thespecial position to make proper record of false calls so that theircausefmay be located and remedied.

hat is claimed is: v y, I 1. In a multi-office semi-automatic telephonesystem, a first ofiice and a second .oflice,

operator-controlled senders located in the first office, and meansincluding local trunks and inter-ofii'ce trunks whereby the said senders are used to control the operation of the automatic switches to setup connections local to both oflices. 1 v

2. In a telephone system wherein connections areset up through automaticswitching,

mechanism controlled from. an operatorsv I switchboard through theintermediary of register senders at such switchboard, operators commonequipment, means for seizing sald register senders at random as callsare initiated, and meansit'or automatically connectmg the associatedcommon equlpment with any se1zed sender. 1

3. In a telephone system wherein register senders are provided forcontrolling automatic switches, an operators switchboard, a plurality ofregistersenders at said switchboard accessible to calling lines, adistributing device atsaid switchboard having ac.-

cess to each of said senders, and means responsive to the seizure of oneof said senders for advancing said distributing device and for bringingit to rest in association with the seized sender. V

4. In a telephone senders are provided for controlling automaticswitches, an operatorsswitchboard, a plurality of register senders'atsaid switchboard accessible to calling lines, a distrib-- uting deviceat said switchboard having access to each of said senders, meansresponsive to the seizure of one of said senders for advancing saiddistributing device and for bringing it to rest in association with theseized sender, operators common eqmpment,

a connecting relay associated wit-h' each of said senders, and'means'controlledfby said distributing device when it finds a seized sender foroperating theconnecting relay of such sender'to connect the operatorscom-:

i switchboard, a common talking circuit com;

system wherein register prising two sections the first of which extendsto the operators telephone, a plurality of individual talking circuitsterminating at said switchboard, automatic means for extendingconnections from subscribers lines to any one of said individual talkingcircuits, means in cluding a hunting device responsive to a connectionextended to one of said individual talking circuits, for impressing atone current on the second section of said common talking circuit andfor starting said distributor to connect the seized individual talkingcircuit with the second section of said common talking circuit, andmeans effective a moment after the said connection is effected fordiscontinuing the application of tone current to the said second sectionof the common talking circuit and for uniting the two sections so thatthe operator may converse with the calling subscriber.

' 6. In a remotely-controlled semi-automatic exchange system, meansresponsive to the initiation of a call on a line terminating in aremotely-controlled semi-automatic exchange for extending such line toan automatic'directive switch, an operating trunk extending fromtheremotely controlled exchange to an operating point, means responsiveto the said initiation of a call for associating said operating trunkwith the said directive switch and for establishing a switch-controlcircuit over said operating trunk, means including a sending device atthe operatlng point for interrupting the control c1rcu1t over saidoperating trunk to set up a desired connection through said directiveswitch,and means controlled from the operating point over the controltrunk after the connection has been set up for causing a switch-throughoperation in the semiautomatic exchange and the freeing of the operatingtrunk thereat, while maintaining a current flow over the. controlcircuit until theswitch-through operation has been ef- 'fected.

7. In a remotely-controlled semi-automatic exchange system, meansresponsive to the initiation of a call'on a line terminating in aremotely controlled semi-automatic exchange for extending such line toan automatic directive switch, a two conductor operating trunk extendingfrom the remotely controlled exchange to an operating point, meansresponsive to the said initiation of a a call for associating saidoperating trunk with the said directive switchand for establishing-aswitch-control circuit over said operating trunk, means including asending device at the operating point for interrupting the controlcircuit over said operating trunk to set up a desired connection throughsaid directive switch, and means controlled from the operating pointover said operating trunkto switch the connection through at thesemi-automatic exchange and to free the associated end of the operatingtrunk by unbalancing the current fiow'in the tw conductors of theoperating trunk.

' 8. In a remotely-controlled semi-automatic exchange system wherein theswitching apparatus in a semi-automatic exchange is controlled over anoperating trunk from a contl'ol point, the operating trunk beingassociated successively with trunk lines over which connections are tobe set up, means responsive to the association of the operating trunkwith a local trunk when a connection is to be set up thereover forestablish-' ing an unbalanced current flow over theopcrating trunk,means at the control point responsive to such unbalanced flow forsignalling the operator at the control point.

' 9. In a remotely-controlled semi-automatic exchange system wherein theswitching apparatus in a semi-automatic exchange is con trolled over anoperating trunk being asso' ciated successively with trunk lines overwhich connections are to be set up, means responsive to the associationof the operating trunk with a local trunk when a connection is to be setup thereover for establishing an unbalanced current flow over theoperating trunk, means at the control point responsive to suchunbalanced flow for signalling the operator at the control point, andmeans responsive to the extension of the connection from the controltrunk to the operators equipment for balancing the current flow over theoperating trunk.

10. In a remotely controlled semi-automatic exchange system wherein theswitching apparatus in a semi-automatic exchange is controlled over anoperatingtrunk from a controlled point, the operating trunk beingassociated successively with trunk lines over which connections are tobe set up, means responsive to the association of the operating trunkwith a local trunk when a connection is to be set up thereover forestablishing an unbalanced current flow over the operating trunk, meansat the control point responsive to such unbalanced flow forsignallingthe operator at the control point, means responsive to the extension oftheconnection from the control trunk to the operators equipment forbalancing the current flow over the operating trunk, and meansresponsive thereto for removing the release of the connection from underthe control of the calling line.

11. In a remotely controlled semi-auto unbalanced current flow overtheoperating trunk, means at the control point responsive to suchunbalanced flow for signalling the operator at the control point, meansresponsive to the extension of the connection from the control trunk tothe operators equipment for balancing the current flow over theoperating trunk, means responsive thereto for removing the release ofthe connection from underthe control of the calling line, and meansresponsive to a further unbalanced con-. dition of the operating trunkafter the control has been exercised from the operating point forswitching the connection through from the calling line to the set upconnection through the automatic switches and for disassociating theoperating trunk from the local trunk line.

12. In a semi-automatic telephone system wherein a remotely controlledsemi-automatic exchange is controlled over a two-conductor operatingtrunk extending between that exchange and an operating point, whichtrunk is associated with calling lines successively in thesemi-automatic exchange, means controlled over the two operatingtrunkconductors for setting the switches in the semi-automatic exchange, andmeans responsive to current flow over one conductor only of theoperating trunk for freeing the operating trunk from an establishedconnec tion.

13. In a semi-automatic telephone system wherein a remotely controlledsemi-automatic exchange is controlled over a two-conductor operatingtrunk extending between that exchange and an operating point, whichtrunk is associated with the calling lines successively in thesemi-automatic exchange,

means controlled over the two operatingtrunk conductors for setting theswitches in the semi-automatic exchange, means for stopping the currentflow over one conductor of the operating trunk while permitting thecurrent flow over the other conductor thereof, and means responsivetheretofor freeing the operating trunk from the established connectionand for switching such connection through and placing it under thecontrol of the calling line.

14. In a multi-ofiice automatic telephone system, a group of registersenders located in a first oifice, operators setting equipment common tosaid register senders, means responsive to current flow over oneconductor ing line local to said first oifice or on a calling line localto a second oflice for associating an idle one of said register senderswith the calling line, and means for thereupon associating the operatorscommon setting equipment with the last named register sender.

15. In a multi-oflice semi-automatic telephone system, a first ofiiceand a second office, automatic switches in each office arranged toextend calling lines directively, register senders in the second oflicearranged to exercise directive control over said automatic switches, atrunk line connecting said otfices, means responsive to a call on a linein the second oifice for extending a connection to one of said automaticswitches and for ex-v tending a branch connection directly to an idleone of said register senders, and means responsive to a call on a linein the first office for extending a connectionto one of said an: tomaticswitches and for extending a branch connection by way of saidinter-ofiice trunk line to an idle one of said register senders.

16. In a multirofi'ice semiautomatic telephone system, a first oificeand a secondofiice, automatic switches in each oifice arranged to extendcalling lines directively, trunk lines in the second 'oflice extendingto an operators switchboard, an interoflicetrunk line extending from thefirst oflice to the second oifice, means responsive to a call on a linein the second oifice for extending a connection to One of said automaticswitches in the second I operator for operating the automatic switch oneof said automatic switches inthe second officeand for extending a branchconnection directly to an idle one of said trunk lines leading to theoperators switchboard, means responsive to a callo'n theline in thefirst oifice for extending a connection to one of said automaticswitchesin the first oifice and for extending a branch connection by way of saidinteroffice'trunk line to an idle one of said trunk lines leading to theoperators switchboard, and means for enabling the operator at saidswitchboard'to converse with the subscriber on either of said callinglines over the branch connection and for operating the automaticswitchto which the calling'line is connected. I i

18. In a telephone system, an operators switchboard, a plurality oftrunk lines at said operators switchboard, talking conductors at saidswitchboard individual to the operators headset and common to said trunklines, means for extending connections from calling subscribers lines toidle ones of said trunk lines, means for connecting the said headsetconductors to any one of said trunk lines, and means for thereuponmaking a momentary'application of tone current to the said headsetconductors to inform the cal ing subscriber on the calling line that heis in communication with the operator.

19. In a semi-automatic telephone system, trunk lines over whichtelephone connections are set up through the medium of automaticswitches, register senders for controlling the automatic switches to setup the said telephone connections link circuits arranged to interconnectsaid trunk lines and said register senders, operators equipment commonto said link circuits and including a group of digit keys and a startkey, means for setting up a connection between one of said trunk linesand one of said register senders by Way of one of said link circuits,means for setting up a connection from the operators common equipment tothe last named link circuit and register sender, said last meansincluding a distributing device having access to each of said registersenders, registering means in the connected register sender responsiveto successive manipulations of the operators digit keys for registeringthe digits of a desired number, means responsive to an opera tion of theoperators start key for starting the register sender to retransmitdigits by Way of the connected trunkline to cause the desired connectionto be set up by way of automatic switches, and means in the connectedlink circuit responsive to the release of said start key following itsoperation for advancing said distributing device to dis associate theoperators common equipment from the link circuit and connected registersender.

20. In a semi-automatic telephone system, trunk lines over whichtelephone connections are to be set up through the medium of automaticswitches, register senders for controlling said automatic switches,operators common equipment for controlling said registersendersincluding digit keys and the start key, a distributing deviceassociated with the operators common-equipment and having access to allof said register senders, means responsive to a calling condition on anyone of said trunk lines for connecting any idle one of said registersenders to such trunk line and for operating said distributing device toconnect the operators common equipment to the connected register sender,registering means in the connected register sender responsive toactuations of the operators digit keys to store digits of a desiredtelephone number, and means. responsive to an operation of said startkey for starting the register sender to transmit the stored digits tothe automatic switches by Way of said

